Method and apparatus for producing hydrogen from methanol

ABSTRACT

A method that allows producing hydrogen from methanol in a simple manner and an apparatus that is small in size and light in weight, which can produce hydrogen from methanol, are provided. The apparatus comprises a container ( 4 ) that retains liquid methanol ( 2 ) as a source material and gases ( 3 ) generated therein, a substrate ( 5 ) that is immersed in liquid methanol ( 2 ) in the container ( 4 ) loaded with a catalyst, and a power supply ( 6 ) for passing a direct or an alternating current through the substrate ( 5 ). The substrate may be made of an oxide or oxidized material, especially oxidized diamond, and loaded with a transition metal catalyst, especially Ni catalyst. With the substrate ( 5 ) heated, a novel catalytic methanol decomposition reaction occurs by a combination of abrupt temperature gradient directing towards methanol from the surface of the substrate, a catalysis of the oxide or oxidized material of the substrate and a catalysis of the catalyst loaded on the substrate, and a large amount of hydrogen gas is produced.

TECHNICAL FIELD

The present invention relates to a method of producing hydrogen frommethanol and an apparatus for producing hydrogen from methanol, which issmall in size and light in weight.

BACKGROUND ART

A fuel cell is a power source that outputs electric energy directlyconverted from chemical energy of the fuel, therefore its energyconversion efficiency is high, and consequently it is anenvironment-friendly power source. Among fuel cells, a fuel cell of thetype using hydrogen and oxygen as the fuels is becoming practical use asa pollution-free power source mainly for automobiles, because theirreaction product is water.

Now, in the automobiles having such a fuel cell as their power source,there are systems, one of which carries a cylinder filled with a highpressure hydrogen gas and uses hydrogen gas thereof as a fuel, and theother of which carries a fuel such as petroleum or methanol and uses thehydrogen produced by a hydrogen producing apparatus so called fuelreformer from fuel thereof.

Since hydrogen gas has an extremely large risk of explosion by mixingwith air, it is more desirable for safety to use the system whichcarries a fuel such as petroleum or methanol and produce only anecessary amount of hydrogen gas from fuel thereof when needed, than touse the system which carries a cylinder filled with a high pressurehydrogen gas and use hydrogen gas thereof.

However, since a conventional hydrogen producing apparatus is large insize and consumes a large amount of energy for hydrogen producing, therehas not been the practical use for automobiles or the like. Mentionthereof may be made more specifically by referencing to an exemplaryhydrogen producing apparatus in the prior art.

FIG. 5 is a diagrammatic view of a conventional hydrogen producingapparatus for producing hydrogen gas from methanol. In the Figure,liquid methanol 51 is introduced into a methanol vaporizer 53 heated toa temperature of about 300° C. by a heater 52 such as a burner to bevaporized into methanol gas 54, and the methanol gas 54 is introducedinto a catalyst bed 55. As catalyst bed 55 has a layer structure ofcatalyst 56 comprising catalyst particles 56 of Pd/CeO₂ or the likewhich can decompose methanol into hydrogen gas and other gaseouscomponents mainly including carbon dioxide gases, the vaporized methanol54 introduced into the catalyst bed 54 is decomposed by the catalyst 56into hydrogen and other gases mainly including carbon dioxide 57. Thecatalyst bed 55 needs to be heated for activating the catalyst 56 to atemperature of about 300° C. by a heater 52 such as a burner. Hydrogenand other gases mainly including carbon dioxide 57, which are producedthrough the decomposition by the catalyst bed 55, are introduced into aseparator 58 where they are separated into hydrogen gas 60 and othergases 59 whereby hydrogen gas 60 is produced. The separator 58 may, forexample, be a selective adsorber adapted to selectively adsorb carbondioxide gas.

In the vaporizer 53 of the apparatus, however, it is necessary tomaintain the vaporizer 53 as a whole at the high temperature of about300° C. by heating for maintaining the vaporizing rate always high, bywhich producing immediately when needed, an amount of hydrogen gasneeded for generating a driving force of the automobile, and it has thesize which can not be ignored as compared with the size of automobile.

Also, in the catalyst bed 55 of the apparatus, however, it is necessaryto maintain the catalyst bed 55 as a whole at the high temperature ofabout 300° C. by heating for maintaining the reaction rate of thecatalyst always high, by which producing immediately when needed, anamount of hydrogen gas needed for generating a driving force of theautomobile, and it has the size which can not be ignored as comparedwith the size of automobile.

Thus, the conventional hydrogen producing apparatus is too large in sizeand in weight, and consumes too much energy for heating the vaporizerand the catalyst bed, to be equipped in practice for any automobile.

DISCLOSURE OF THE INVENTION

With the aforementioned problems taken into account, it is an object ofthe present invention to provide a method of producing hydrogen frommethanol in a simple manner and an apparatus that is small in size andlight in weight, which can produce hydrogen from methanol.

In order to achieve the above objects, there is provided in accordancewith the present invention a method of producing hydrogen from methanolcharacterized in that it comprises a step of heating a substrate loadedwith a catalyst in liquid methanol to produce hydrogen gas.

Said catalyst is preferably a catalyst made of a transition metalelement, especially Ni catalyst.

Said substrate loaded with the catalyst is preferably an oxide oroxidized substrate made of a material which can be selected from thegroup which consists of oxidized diamond, silicon dioxide, zirconiumdioxide, activated carbon, cerium dioxide and titanium dioxide.Alternatively, said substrate loaded with the catalyst is preferablyactivated carbon. Also, said substrate preferably has an electricconductivity or has a resistive substance, through which by passing acurrent, said heating of the substrate is performed. Said substrate isheated preferably to a temperature of 300° C. or more.

The present invention further provides an apparatus for producinghydrogen from methanol, characterized in that it comprises: a containerfor holding liquid methanol; a substrate loaded with a catalyst, whichis immersed in said liquid methanol; and a substrate heating means forheating said substrate, wherein said substrate in said liquid methanolis heated, gases are produced at the surface of said heated substrate,the gases are taken out, and hydrogen gas is obtained by gas separationmeans from said taken out gases.

The present invention further provides an apparatus for producinghydrogen from methanol, characterized in that it comprise: a containerfor holding liquid methanol; a substrate loaded with a catalyst; and asubstrate heating means for heating said substrate, in which saidcatalyst is made of a transition metal, and said substrate is an oxideor oxidized substrate or activated carbon substrate, wherein saidsubstrate is heated in said liquid methanol, gases are produced at thesurface of said heated substrate, the gases are taken out, and hydrogengas is obtained by gas separation means from said taken out gases.

Said catalyst made of a transition metal is preferably Ni catalyst.Also, said oxide substrate preferably is made of oxidized diamond.Alternatively, said oxide substrate may preferably be made of a materialselected from the group which consists of silicon dioxide, zirconiumdioxide, cerium dioxide and titanium dioxide.

Said substrate heating means comprises an electric power supply forpassing an electric current through said substrate or said resistivesubstance. Said oxide or activated carbon substrate is heated preferablyto a temperature of 300° C. or more.

According to the method and apparatus of the present invention, byheating the substrate loaded with the catalyst in liquid methanol, anabrupt temperature gradient directing towards the liquid methanol from asurface of the substrate is created, and by a combination of this abrupttemperature gradient, the catalysis of the substrate and the catalysisof the catalyst loaded on the substrate, a novel methanol decompositionreaction is yielded, and by this methanol decomposition reaction,methanol surrounding the surface of the substrate is decomposed togenerate hydrogen gas. If the substrate is made of an oxide or oxidizedmaterial, in particular oxidized diamond and the catalyst comprises Ni,then the hydrogen production efficiency is eminently high.

Thus, the method of the present invention allows producing hydrogen inthe simple manner only to heat a substrate loaded with a catalyst inmethanol, hence it requires only one container instead of hithertoindispensable two containers, one for methanol vaporization and one formethanol decomposition in the conventional apparatus, thereby it becomespossible to make the apparatus to be small.

Moreover, the reaction rate of the novel methanol decomposition reactionwhich is yielded by the combination of abrupt temperature gradientdirecting towards the liquid methanol from the surface of substrate, thecatalysis of oxide or oxidized substrate, and the catalysis of catalystloaded on the substrate, is extremely higher than that of conventionalreaction, hence it is possible to make the apparatus small in size andweight comparing with the conventional apparatus having the samehydrogen producing rate. Also, the reaction rate of the novelmethanol-decomposition reaction which is yielded by the combination ofthe abrupt temperature gradient directing towards the liquid methanolfrom the surface of substrate, the catalysis of oxide or oxidizedsubstrate and the catalysis of catalyst loaded on the substrate, isextremely high, hence the consumption energy required to producehydrogen is small.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will better be understood from the followingdetailed description and the drawings attached hereto showing certainillustrative forms of implementation of the present invention. In thisconnection, it should be noted that such forms of implementationillustrated in the accompanying drawings hereof are intended in no wayto limit the present invention but to facilitate an explanation andunderstanding thereof. In the drawings,

FIG. 1 is a diagram illustrating the makeup of an apparatus forproducing hydrogen from methanol in accordance with the presentinvention;

FIG. 2 is a graphic chart illustrating the hydrogen productionefficiency obtained in the method using the substrate made of oxidizeddiamond and the catalyst varied variously;

FIG. 3 is a graphic chart illustrating the hydrogen productionefficiency obtained in the method using Ni metal catalyst and thesubstrate varied variously;

FIG. 4 is a graph illustrating how the hydrogen production efficiencydepends on the substrate temperature; and

FIG. 5 is a diagram illustrating the makeup of a hydrogen producingapparatus in the prior art.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail withreference to forms of implementation thereof illustrated in the drawingfigures. Mention is made of a method of producing hydrogen from methanolusing an apparatus according to the present invention.

FIG. 1 is a diagram illustrating the makeup of an apparatus forproducing hydrogen from methanol in accordance with the presentinvention, wherein the same reference characters are used to designatethe same members or components.

An apparatus 1 for producing hydrogen from methanol in accordance withthe present invention comprises a receptacle or container 4 that holdsliquid methanol 2 and gases 3 generated therein, a substrate 5 loadedwith a catalyst, which is immersed in liquid methanol 2 of container 4,and a power supply 6 for passing a direct or an alternating electriccurrent through substrate 5 to heat the substrate. While in form of theimplementation it is shown that the substrate heating means is anelectric power supply for passing the electric current through substrate5, it may be any other means that can heat the substrate, such as aheater, for example.

Substrate 5 is made of an oxide or oxidized material, and loaded by thecatalyst of a transition metal. For example, the substrate which is madeof the steps of vapor-depositing a transition metal on a substrate madeof an oxide or oxidized material and reduction-treating in hydrogen, isusable.

In an operation of this hydrogen producing apparatus 1 described above,liquid methanol 2 is supplied into container 4 through its methanolinlet port 4 a so that substrate 5 is immersed in liquid methanol 2.Then, with supplying the electric current from power supply 6 throughelectric wires 6 a, substrate 5 is heated to a temperature of 300° C. ormore preferably as later described. When substrate 5 is heated, bubblesof gases 3 comprising mainly hydrogen gas are vigorously generated fromthe surfaces of substrate 5. Gases 3 are taken out or collected throughgas outlet port 4 b. Gases 3 taken out contain mainly hydrogen gas,carbon monoxide gas and very small amount of other gases such as carbondioxide and methane. Then, by separating the gases taken out through aknown gas separator, hydrogen gas is obtained.

As the hydrogen producing apparatus described above can decomposemethanol 2 and produce gases 3 mainly containing hydrogen gas, only byheating the substrate 5 loaded with the catalyst, it requires only onecontainer in stead of the hitherto indispensable two containers, one formethanol vaporization and one for methanol decomposition in aconventional apparatus as mentioned hereinbefore, hence it is possibleto make the apparatus to be small in size. Moreover, as the methanoldecomposition reaction of the method of the present invention iseminently higher in reaction rate, as will be shown in the specificexample below, than that of the conventional method in which vaporizedmethanol is decomposed by catalyst, it is possible to produce asufficient amount of hydrogen gas, even if the apparatus is made smallerin size. And for the same reason, the consumption energy to producehydrogen is small.

While a precise mechanism of the methanol decomposition reaction of themethod of the present invention has not been yet fully elucidated, itappears that the novel methanol decomposition reaction occurs by thecombination of the abrupt temperature gradient directing towards liquidmethanol from the surface of the substrate, the catalysis of thesubstrate made of oxide or oxidized material and the catalysis of thecatalyst loaded on the substrate.

Mention is next made of a specific example.

Conversion efficiencies were compared, which are measured by using theapparatus of the present invention as shown in FIG. 1 by changing thekinds of the substrates and the catalysts loaded thereon. The substratesused are oxidized diamond (O-dia), silicon dioxide (SiO₂), zirconiumdiode (ZrO₂), activated carbon (AC), cerium diode (CeO₂), titanium diode(TiO₂), alumina (Al₂O₃) or magnesium oxide (MgO), and the catalystsloaded on the substrate are Ni, Co, Rh, Ir, Cu, Pt or Ru.

The experiment was executed by using the substrate which was preparedfor every combinations of the above mentioned substrates and thecatalysts by forming a thin film of the catalytic metal on the substrateby sputtering, vapor deposition or impregnation, and followed withreducing the surface of the substrate in hydrogen gas atmosphere. Ineach the experiment, the electric current through the substrate wascontrolled so that the substrate has a fixed temperature of 300° C., andmeasurements were made on the amount of gases generated in a time periodof 30 minutes and also on the composition ratio of the gases.

FIG. 2 is a graph illustrating the conversion efficiencies of methanolinto hydrogen, which were obtained for the substrate of oxidized diamondand for every catalysts of Ni, Co, Rh, Ir, Cu, Pt or Ru. In the graph,the ordinate axis in the right hand side represents the conversionefficiency, the abscissa axis represents the kind of the catalysts andthe ordinate axis in the left hand side represents the composition ratioof the gases, respectively. In the chart, the line graph represents theconversion efficiencies and the bar graph represents the compositionratios of the gases. Here, the conversion efficiencies and thecomposition ratios are represented by mol ratio, and the units of theordinate axes are arbitrary scales for relative comparison.

As can be seen from the graph, a highest conversion efficiency isachieved with the catalyst of Ni, The composition ratio of the Gasescomprises with the range of 60 to 70% of hydrogen gas and the residue ofcarbon monoxide, carbon dioxide and methane.

FIG. 3 is a graph illustrating the conversion efficiencies of methanolinto hydrogen which were obtained for the catalyst of Ni and for everysubstrates of oxidized diamond (O-dia), silicon dioxide (SiO₂),zirconium diode (ZrO₂), activated carbon (AC), cerium diode (CeO₂),titanium diode (TiO₂), alumina (Al₂O₃) or magnesium oxide (MgO). In thegraph, the ordinate axis in the right hand side represents theconversion efficiency, the abscissa axis represents the kind of thesubstrates and the ordinate axis in the left hand side represents thecomposition ratios of the gases, respectively. In the chart, the linegraph represents the conversion efficiencies and the bar graphrepresents the composition ratios of the gases. Here, the conversionefficiencies and the composition ratios are represented by mol ratio,and the units of the ordinate axes are arbitrary scales for relativecomparison.

As can be seen from the graph, a highest conversion efficiency isachieved when the substrate is made of oxidized diamond. The compositionratios of the Gases comprises the range of 60 to 70% of hydrogen gas andthe residue of carbon monoxide, carbon dioxide and methane.

FIG. 4 is a graph illustrating the dependency of the conversionefficiency on the temperature of the substrate. The dependency wasobtained for the substrate of oxidized diamond and the catalyst of Ni.In the graph, the ordinate axis represents the conversion efficiency,the abscissa axis represents a temperatures of the substrate, and thescale of ordinary axis is an arbitrary scale for relative comparison.

From this graph it is seen that a sufficient conversion efficiency isobtained when the substrate has a temperature of 300° C. or more.

From the specific example above, it is seen that an eminent hydrogenproducing efficiency is obtained for the substrate composed of oxidizeddiamond, the catalyst composed of Ni and the substrate having atemperature of 300° C. or more.

Additionally, the term “oxidized diamond” used herein is intended tomean a diamond in which dangling bonds of carbon atom of its surface areterminated with oxygen.

INDUSTRIAL APPLICABILITY

As will be appreciated from the foregoing description, the method of thepresent invention allows producing hydrogen in the simple manner to heata substrate loaded with a catalyst in methanol, hence it does requireonly one container instead of the hitherto indispensable two containers,one for methanol vaporization and one for methanol decomposition in theconventional apparatus, thereby it is possible to make it small in sizeand in weight. Moreover, the novel catalysis of methanol-decompositionis extremely high in rate of reaction, which is yielded by thecombination of the abrupt temperature gradient directing towards liquidmethanol from the surface of substrate, the catalysis of the substratemade of an oxide or oxidized material and the catalysis of a catalystloaded on the substrate, hence it is possible to make the apparatussmaller in size and weight than the conventional one having the samehydrogen producing rate. Also, such an extremely high reaction rate ofthis novel catalysis of methanol decomposition, which is yielded by thecombination of the abrupt temperature gradient directing towards liquidmethanol from the surface of substrate, the catalysis of the substratemade of an oxide or oxidized material and the catalysis of a catalystloaded on the substrate, reduces the energy consumption required toproduce hydrogen. The present invention is therefore extremely usefulwhen used such a field of automobiles of which the power is supplied bya fuel cell.

1-16. (canceled)
 17. A method of producing hydrogen from methanol,characterized in that it comprises of heating a substrate loaded with acatalyst in liquid methanol, wherein the substrate is made of a materialselected from the group which consists of oxidized diamond, silicondioxide, zirconium dioxide, cerium dioxide, titanium dioxide andactivated carbon, and the catalyst is a catalyst selected from the groupwhich consists of Ni, Co, Rh, Ir, Cu, Pt, and Ru, wherein abrupttemperature gradient directing from said substrate surface toward saidliquid methanol is formed, and a methanol decomposition reaction yieldedby said abrupt temperature gradient, the catalytic reaction of saidcatalyst, and by the catalytic reaction of said substrate decomposesmethanol to generate hydrogen gas.
 18. A method of producing hydrogenfrom methanol as set forth in claim 17, characterized in that saidsubstrate loaded with a catalyst is the substrate having electricconductivity, or the substrate having a resistive substance, and themeans of said heating a substrate is an electrical power supplying meansfor heating by supplying electric current to said substrate havingelectric conductivity, or said substrate having a resistive substance.19. A method of producing hydrogen from methanol as set forth in claim17 or 18, characterized in that said substrate loaded with a catalyst isheated over 300° C.
 20. An apparatus of producing hydrogen from methanolcharacterized in that it comprising: a container for holding liquidmethanol and generated hydrogen gas provided with methanol inlet portfor supplying liquid methanol and outlet port for taking out thegenerated hydrogen; a substrate made of a material selected from thegroup consisting of oxidized diamond, silicon dioxide, zirconiumdioxide, cerium dioxide, titanium dioxide and activated carbon; acatalyst loaded on said substrate, which is a catalyst selected from thegroup consisting of Ni, Co, Rh, Ir, Cu, Pt, and Ru, and a means forheating said substrate, whereby heating said substrate forms abrupttemperature gradient directing from said substrate surface toward saidliquid methanol, and methanol decomposition reaction yielded by saidabrupt temperature gradient, the catalytic reaction of said catalyst,and by the catalytic action of said substrate decomposes methanol togenerate hydrogen gas.
 21. An apparatus of producing hydrogen frommethanol as set forth in claim 20, characterized in that said substrateloaded with a catalyst is the substrate having electric conductivity, orthe substrate having a resistive substance, and the means for heatingsaid substrate is an electrical power supplying means for heating bysupplying electric current to said substrate having electricconductivity, or said substrate having a resistive substance.